The present invention pertains to a pressure sensor and a method of manufacturing the same, and in particular to an electrical capacitance-type diaphragm pressure sensor for sensing a fluid pressure in, for example, a container for chemicals, a pipe for chemicals, and the like, and a method of fabricating the same.
Conventional pressure sensors for sensing a fluid pressure in a container for chemicals, a pipe for chemicals, and the like, are provided with a diaphragm which acts as a pressure-sensing means, whereby deflection of the diaphragm in response to an applied pressure is translated into an electric signal, to thereby sense a pressure.
Japanese Patent Application No. 2002-130442 discloses as an example of such a diaphragm pressure sensor “Electrical capacitance-type diaphragm pressure sensor”.
Such a diaphragm pressure sensor normally comprises: a pressure-sensing member provided with a pressure receiving part including strip diaphragms provided in opposing relation, and deposited electrodes formed on opposing surfaces of the diaphragms; and a housing member for enclosing the pressure receiving part of the pressure-sensing member, the housing member being made of a material resistant to corrosion by a fluid whose pressure is to be detected by the sensor.
Such a diaphragm pressure sensor is constituted such that when immersing a housing member in a fluid whose pressure is to be sensed, a fluid pressure acts on the pressure receiving part, and any resulting variations in a distance between opposing diaphragms causes a change in capacitance.
In a conventional diaphragm pressure sensor such as that described above, a gap is formed between a pressure receiving part of a pressure-sensing member and a housing member for enclosing the pressure-sensing member, so that a pressure acting on the housing member is transferred to the pressure receiving part of the pressure-sensing member via an applied pressure transfer material filling the gap. As an applied pressure transfer material used for filling such a gap, a silicone adhesive has been conventionally employed. Therefore, as a temperature of a fluid, etc. whose pressure is to be sensed changes, a pressure transfer coefficient varies, which results in drift, loss of linearity of a pressure transfer coefficient, and by extension, inaccurate operation of the pressure sensor.